(1) Field of Invention
The present invention relates to a hydrogen system comprising a hydrogen generator and a hydrogen consumer and a method for starting up such a hydrogen system.
More specifically, the invention relates to a device and a method for generation of electric energy with or without utilization of produced heat energy. The invention is based on a combination of generation of electric energy and/or heat wherein the hydrogen consumer may comprise a high temperature PEM-fuel cell to operate with process gas from an autothermal reformer using fuel in the form of liquid hydrocarbon fuel oils, diesel, bio-fuels or other suitable liquid fuels. The invention may be utilised as an APU system and/or combined heat and power production. By the term PEM fuel cell we mean proton exchange membrane fuel cells, which uses hydrogen fuel and oxygen, preferably from air, to produce electricity. Rather than comprising a fuel cell, the hydrogen consumer may also comprise other forms of equipment like equipment for production of ammonium or other processes requiring hydrogen and/or carbon monoxide and/or carbon dioxide.
(2) Description of Related Art
When a hydrogen generating system is used with a fuel cell, the HT-PEM fuel cell has some advantages over standard PEM fuel cells. The combination of a reformer reforming a liquid fuel to a syngas/reformer gas and a high-temperature PEM fuel cell is advantageous over fuel cells known from prior art working at lower temperatures in that the membranes in high-temperature PEM cells is considerably more resistant to carbon monoxide (CO) than the membranes in PEM fuel cells. This is very beneficial compared to low temperature PEM cells which in practice has no tolerance for CO, and for which strict measures for removing this gas component needs to be introduced. This can, in addition to the water shift reactor, be initial oxidation (also called SelOx, Selective Oxidation) for removing/oxidizing the CO in the reformate feed to prevent the PEM fuel cell from becoming poisoned with CO. These measures are difficult to control, and thus lead to higher costs (for example there is a need of two more catalysts).
One of the disadvantages of known HT-PEM fuel cell systems is that since they have a higher operating temperature, thus it takes longer to warm up the fuel cell system to its operating temperature when it is cold-started. Known HT-PEM fuel cell systems from the prior art takes 45 minutes and more to warm up which can be a serious disadvantage for many applications where a shorter start-up time is required.